Single fundamental-mode output power exceeding 6 mW from VCSELs with a shallow surface relief

A single fundamental-mode output power of 6.5 mW was achieved from an 850-nm vertical-cavity surface-emitting laser (VCSEL) with a shallow surface relief, the highest single-mode power ever reported using this technique. The VCSELs were fabricated from epitaxial material grown to yield an antiphase reflection from the topmost layer. A circular surface relief, acting as a mode discriminator, was etched in the center to reduce the mirror loss for the fundamental mode. This "inverted" surface-relief technique offers relaxed etch depth control and, therefore, improves reproducibility and yield.     

Linear crosstalk in 4×4 semiconductor optical amplifier gateswitch matrix

We report a comprehensive crosstalk investigation of a packaged InGaAsP/InP 4×4 semiconductor optical amplifier gate switch matrix, experimentally as well as theoretically. For a fully loaded switch with the same wavelength on all four inputs, all possible switching combinations are analyzed, thus yielding realistic crosstalk figures. Coherent and incoherent crosstalk phenomena are identified, and a switch crosstalk less than -40 dB has been measured     

Solid-state13C NMR investigations of insoluble deposits in aromatic bitters

Insoluble deposit formed in aromatic bitters produced from alcoholic extracts of about 30 different botanical materials with a dry matter content of 1.67% and 38 vol% alcohol and a characteristic astringent flavour was shown by¹³C NMR spectroscopy to be a coprecipitate of plant polyphenols, proteins and carbohydrates. The polyphenols in the deposit were flavonoids such as anthocyanidins and anthocyanins, with glucose as the principal carbohydrate and derivatives of cinnamic acid. The deposit formation in the aromatic bitters was accelerated by addition of the radical initiator 2,2′-azobis(2-amidinopropane) dihydrochloride or by addition of hydrogen peroxide in combination with iron(III) nitrate and ascorbic acid as a Fenton reagent. Polymerization of catechin and pelargonidin was shown, in model experiments, to be oxidative and to be accelerated by exposure to light. A mechanism involving oxidative polymerization of polyphenols followed by coprecipitation of polymerized polyphenols, proteins and carbohydrates is proposed for formation of deposits in alcoholic beverages of the bitters type.     

Notch sensitivity of thermoset and thermoplastic laminates loaded in tension

Inplane tensile fracture of unnotched and notched thermoset graphite-epoxy and thermoplastic graphite-PEEK composite laminates is examined. Both fibre-dominated quasi-isotropic and matrix dominated ±45 angle-ply layups were investigated.Classical lamination theory predictions of elastic and strength properties of unnotched specimens are compared with experiments. Several notched geometries, i.e. centre-notched, double-edge notched and open-hole specimens subjected to tensile loading to fracture were examined. The notched strength of the quasi-isotropic laminates was analysed by a damage zone model, where damage around the notch is represented by an equivalent crack with cohesive force acting between the crack surfaces.Good agreement between experimental and calculated strength was observed for the graphite-epoxy laminates which failed in a collinear manner. For the graphite-PEEK laminates discrepancies between predicted and experimental strength are related to observed deviations from collinear crack growth. The angle-ply graphite-PEEK laminates showed larger notch sensitivity than the corresponding graphite-epoxy, probably due to less degree of stress relieving damage formation around the notch.     

Storage life of frozen salmonoids Effect of light and packaging conditions on carotenoid oxidation and lipid oxidation

Summary The combined effect of oxygen transmission of packaging material and of exposure to light with different spectral distribution on the oxidative degradation of carotenoids and lipids in frozen salmonoids has been characterized in a storage experiment with steaks of rainbow trout. The degradation of the carotenoid astaxanthin, as followed by HPLC analysis and tristimulus colorimetric measurement, was sensitive to the radiant flux density of UV light and less sensitive to the oxygen transmission rate of the packaging material, in agreement with previous findings for photooxidation of carotenoids in food model systems. This is in contrast to the lipid oxidation, which was found to be dependent on the accessability of oxygen rather than on exposure to UV light. Formation of peroxides in the product culminated after 3 months of storage (up to 8.4 mEq kg^–1 oil), and preceded the formation of thiobarbituric-acid-reactive substances. The product in packaging material with a high oxygen transmission rate (60 cm³ m^–2 bar^–1 per 24 h) reached a level of approximately 5 mol malonaldhyde/kg^–1 product, when stored exposed to standard fluorescent light or fluorescent light with a high UV component. Rancid taste was not detected by sensory evaluation for any of the products after 6 months of storage, whereas a bitter taste was noted for the product exposed to UV light.

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Die Haltbarkeit von Lachsforellen Einfluß von Licht und Verpackung auf die Carotenoid- und Fettoxydation

Zusammenfassung Der kombinierte Effekt von Sauerstoffdurchgang durch Verpackungsmaterial und der Lichteinwirkung verschiedener spektraler Verteilung auf den oxidativen Abbau der Carotinoide und Fette in gefrorenen Lachsforellen wurde in einem Lagerungsversuch untersucht. Der Abbau des Carotenoids Astaxanthin wurde mit HPLC undTristimulus-Calorimetrie beobachtet, und war empfindlich gegenüber UV-Licht und weniger empfindlich gegenüber der Sauerstoffdurchlässigkeit der Verpackung, was mit früheren Ergebnissen für Photooxidation der Carotinoide in Modellsystemen übereinstimmt. Dies widerspricht der Fettoxidation, die mehr von Sauerstoffzugang abhängig ist als von der Entwicklung des UV-Lichtes. Die Bildung von Peroxiden des Produktes kuliminierte nach 3monatiger Lagerung (bis 8,4 meq/kg Öl) und ging der Bildung von Thiobarbitursäure-aktiven Substanzen voraus. Das Produkt im Material mit hohem Sauerstoffdurchgang (60 cm³ m^–2 bar^–1 pro 24 h), das bei normalen fluorescierendem Licht oder bei fluorescierendem Licht mit hohem UV-Anteil aufbewahrt wurde, erreichte einen TBS-Wert von ungefähr 5 mol Malonaldehyd/kg Fleisch. Ein ranziger Geschmack wurde durch sensorische Bewertung nach 6monatiger Lagerung nicht erkannt, wohl aber ein bitterer Geschmack bei dem UV-Licht ausgesetzten Proben.

     

Emission of excited potassium species from an industrial iron catalyst for ammonia synthesis

The angular dependence of potassium emission-desorption is studied from a fused iron catalyst of the type used for ammonia synthesis. The excited species (K^*, K _n ^* , etc.) and positive ions K⁺ have strongly different angular distributions. The bilobular distribution measured for ion desorption is concluded to be either due to excited atoms, so-called Rydberg atoms, or excited clusters. Both types of species have to desorb from the edges of the sample and become field ionized and deexcited just outside the sample, as reported in previous studies on an iron oxide catalyst. The peak in the normal direction measured for excited species is due to excited cluster formation outside the catalyst surface. Similarities with previous results for other catalysts are observed. The possibility that the promoter function of potassium in the ammonia synthesis is due to excited species is pointed out.On leave from Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Cracow, Poland.     

Acid-catalysed reduction of ferrylmyoglobin: product distribution and kinetics of autoreduction and reduction by NADH

The pH dependence of iron(II)/iron(III) product distribution, following reduction of the hypervalent iron in equine ferrylmyoglobin by the protein moiety of the pigment (so-called autoreduction) and by NADH (nicotinamide adenine dinucleotide, reduced) and the rate of reduction was found to depend different on pH. Autoreduction is specific acid catalysed and has a more modest temperature dependence than autoxidation of oxymyoglobin, with the activation parameters H ^#=58.5±0.4 kJ·mol^–1 and S ^#=2.7±0.1 J·mol^–1·K^–1 in 0.16 mol·1^–1 NaCl. The product of autoreduction is the iron(III) pigment metmyoglobin, which is slightly modified in the protein moiety. The reaction has a positive kinetic salt effect from which it is deduced that the reactive centre of ferrylmyoglobin has a charge of +1 in agreement with the structure Fe(IV)=O. Reduction by NADH involves parallel reactions of two pigment forms in acid/base equilibrium with each other with a pK _a equal to 4.9, both forms yielding metmyoglobin as well as the iron(II) pigment, oxymyoglobin, as products. The protonated form reacts faster than the deprotonated form, and two-electron transfer has greater importance for the protonated form with a limiting Fe(II)/Fe(III) product ratio of 0.6 in acidic solution compared to 0.12 in alkaline solution. A square root dependence of rate on NADH concentration suggests involvement of NAD·radicals with a disproportionation as the termination reaction.

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Säure-katalysierte Reduktion von Ferrylmyoglobin. Produktdistribution und Kinetik der Autoreduktion und Reduktion von NADH

Zusammenfassung Die Reaktionsgeschwindigkeit und das Eisen(II)/Eisen(III)-Verhältnis des Produkts nach Reduktion von hypervalentem Eisen in Ferrylmyoglobin aus Pferden zeigt eine unterschiedliche pH-Abhängigkeit der sogenannten Autoreduktion (Reduktion am Proteinteil des Pigments) sowie der Reduktion durch NADH. Die Autoreduktion weist eine spezifische Säure-Katalyse auf sowie eine moderate Temperaturabhängigkeit im Vergleich zur Autooxidation von Oxymyoglobin mit den Aktivierungsparametern H ^#=58.5±0.4 kJ·mol^–1 und S ^#=2.7±0.1 J·mol^–1·K^–1 in 0.16 mol·1^–1 NaCl. Das Produkt der Autoreduktion ist das Eisen(III)-Pigment Metmyoglobin mit leicht modifiziertem Proteinanteil. Die Reaktion hat einen positiv kinetischen Salzeffekt, woraus zu erschließen ist, daß das reaktive Zentrum im Ferrylmyoglobin die Ladung +1 übereinstimmend mit der Struktur Fe(IV)=O besitzt. Die Reduktion durch NADH weist auf parallele Reaktionen von zwei Pigmentformen in einem Säure/Base-Gleichgewicht mit pk _a=4.9 hin, beide Formen ergeben Metmyoglobin sowie das Eisen(II)-Pigment Oxymyoglobin als Produkt. Die protonisierte Form reagiert schneller als die deprotonisierte Form, und eine zwei-Elektronenübertragung hat größere Bedeutung für die protonisierte Form mit einem Fe(II)/Fe(III) Produktverbrauch von 0.6 in der Säurelösung und 0.12 in der Baselösung. Die Quadratwurzel Abhängigkeit der Geschwindigkeit von NADH deutet auf eine Teilnahme von NAD-Radikalen mit Disproportionierung als Schlußreaktion.

     

A little Birdie told me: Social media,organizational legitimacy,and underpricing in initial public offerings

Drawing on the organizational legitimacy literature, we propose and test a set of hypotheses arguing that social media, an artifact of information technology, serves as a mechanism for conferring legitimacy in the market for initial public offerings (IPOs). The extant literature identifies third-party authorities, such as traditional media outlets and industry analysts, as a valuable source of organizational legitimacy. Social media and micro-blogging, however, remain outside current classifications of the phenomenon. This study theoretically develops and empirically tests a new mechanism in the legitimation process: the direct interaction with potential investors and society-at-large via social media. Our findings indicate broad support that having a Twitter account, and the extent to which a firm utilizes Twitter, is associated with systematically higher levels of IPO underpricing. Moreover, we find support that social media variables external to the firm, including number of followers and retweets, also impact the level of underpricing in an IPO. In conclusion, we highlight the emerging role of social media in processes of legitimation and invite additional research at the intersection of IS and management.     

Working conditions in the engine department – A qualitative study among engine room personnel on board Swedish merchant ships

The specific problems associated with the work on board within the merchant fleet are well known and have over the years been a topic of discussion. The work conditions in the engine room (ER) are demanding due to, e.g. the thermal climate, noise and awkward working postures. The work in the engine control room (ECR) has over recent years undergone major changes, mainly due to the introduction of computers on board. In order to capture the impact these changes had implied, and also to investigate how the work situation has developed, a total of 20 engine officers and engine ratings were interviewed. The interviews were semi-structured and Grounded Theory was used for the data analysis. The aim of the present study was to describe how the engine crew perceive their work situation and working environment on board. Further, the aim was to identify areas for improvements which the engine crew consider especially important for a safe and effective work environment. The result of the study shows that the design of the ECR and ER is crucial for how different tasks are performed. Design which does not support operational procedures and how tasks are performed risk inducing inappropriate behaviour as the crew members’ are compelled to find alternative ways to perform their tasks in order to get the job done. These types of behaviour can induce an increased risk of exposure to hazardous substances and the engine crew members becoming injured.